Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02423228 2006-03-08
1
ARCH SYSTEMS
The present invention relates to the general art of structural, bridge and
geotechnical
engineering, and to the particular field of overfilled arch and/or cut-and-
cover structures.
Frequently, overfilled arch structures formed of precast or cast-in-place
reinforced
concrete are used in the case of bridges to support one pathway over a second
pathway,
which can be a waterway, a traffic route, or in the case of other structures,
a storage space or
the like. The terms "overfilled arch" or "overfilled bridge" will be
understood from the
teaching of the present disclosure, and in general as used herein, an
overfilled bridge or an
overfilled arch is a bridge formed of arch elements that rest on the ground or
on a
foundation and has soil or the like resting thereon and thereabout to support
and stabilize the
structure and in the case of a bridge provide the surface of the second
pathway. The arch
form is generally arcuate such as cylindrical in circumferential shape, and in
particular a
prolate shape; however, other shapes can be used. Examples of overfilled
bridges are
disclosed in US Patents 3,482,406 and 4,458,457.
Presently, reinforced concrete overfilled arches are usually constructed by
either
casting the arch in place or placing precast elements, or a combination of
these. These
arched structures rest on prepared foundations at the bottom of both sides of
the arch. The
fill material, at the sides of the arch (backfill material) serves to diminish
the outward
displacements of the structure when the structure is loaded from above. As
used herein, the
term "soil" is intended to refer to the normal soil, which can be backfill
(e.g. soil brought to
and placed in location) or in situ (e.g. soil in its original location),
located at a site used for a
bridge structure, and which would not otherwise adequately support an arch.
The terms
"backfill," and "in situ" will be used to mean such "soil" as well.
Such soil is not adequate to support the concentrated loads at the ends of a
flat arch
or conventional arch without load distribution through the use of arch
footings
CA 02423228 2003-03-20
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and/or reinforced foundation blocks.
Soil is usually not mechanically strong enough to adequately support bridge
structures of interest to this invention. Thus, prior art bridge structures
have been
constructed to transfer forces associated with the structure to walls of the
structure
and/or large concrete foundations at the base of the wall. Such walls have to
be
constructed in a manner that will support such forces and thus have special
construction requirements. As will be discussed below, such requirements
present
drawbacks and disadvantages to such prior art structures.
For the prior art structures, the overfilled arches are normally formed such
that the foundation level of the arch is at the approximate level of a lower
pathway or
floor surface of an underground structure over which the arch spans. Referring
to
Figures 1 A-1 C, it can be understood that prior art systems S 1 and S2
include sides or
sidewalls SW 1 and SW2 which transfer loads from tops T 1 and T2 of the arch
to
foundation F 1 and F2. The sides of arch systems S 1 and S2 must be
sufficiently thick
and contain sufficient reinforcement in order to be able to carry these loads
and the
thereby induced bending moments.
Furthermore, as it is necessary to limit the normal forces, arch loading and
bending actions in the top and sides of prior art overfilled arch systems to
an
acceptable level, the radius of the arch is in practice restricted. This
restriction in
arch radius leads to a higher "rise" R1 and R2 (vertical dimension between the
top of
clearance profile Cl and C2 of lower pathway surface LS 1 or LS2 and crown CR1
and CR2 of the arch) in the arch profile than is often desirable for the
economical
and practical arrangement of the two pathways and formation of the works
surrounding and covering the arch. This results in a lost height LH 1 and LH2
which
can be substantial in some cases.
Beams or slabs, while needing a larger thickness than arches, do not require
this "rise" and, therefore, can be used for bridges accommodating a smaller
height
between the top of the clearance profile of the lower pathway and the top of
the
upper pathway. Arches, despite their economical advantage, often cannot
compete
with structures using beams or slabs for this reason especially for larger
spans.
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However, the larger thickness may result in an expensive structure whose
precast
elements may be difficult unwieldy and heavy to transport to a building site.
Thus,
many of the advantages of this structure may be offset or vitiated.
Furthermore, as indicated in Figures 1 A-1 C, foundations Fl and F2 for the
prior art overfilled arch systems must be substantial in order to carry the
arch loading
indicated in Figure 1 C as AL, and require additional excavation at the base
of the
arch (generally beneath the lower pathway) to enable their construction. As
will be
understood from the present disclosure, forces AL can be considered as being
circumferential forces, and forces AV can be considered as being vertical
forces with
forces AH being considered as horizontal forces. Loading forces on the system
are a
combination of these forces.
Furthermore, the foundations for the prior art overfilled arch systems must be
substantial in order to carry the arch loading and will require additional
excavation at
the base of the arch (generally beneath the lower pathway) to enable their
construction.
For overfilled arches made of precast construction, the incorporation of the
required height of the sides or sidewalls of the arch result either in a tall-
standing
precast element which is difficult and unwieldy to transport and to place or
in the
requirement of pedestals, such as pedestals F 1 a shown in Figure 1 A.
As discussed above, transportation and handling of precast arch elements of
some arch structures are difficult. However, precast elements have certain
advantages including the ability to support their own self-weight and all of
the
advantages associated with pre-casting of such structural elements. However,
precast
elements also have certain disadvantages, including the transportation issues
mentioned above.
Therefore, it would be helpful to retain as many of the advantages associated
with precast structural elements as possible while eliminating, or at least
substantially reducing, as many of the disadvantages associated with precast
structural elements as possible.
Likewise, cast-in-place structural elements have many advantages, including
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the ability to be customized on site and the elimination of the transportation
problems associated with precast structural elements. However, cast-in-place
structural elements also have certain disadvantages, including a need for a
formwork
support structure, as well.
Therefore, it would be expedient to retain as many of the advantages
associated with cast-in-place structural elements as possible while
eliminating, or at
least substantially reducing, as many of the disadvantages associated with
cast-in-
place structural elements as possible.
One aspect of this invention (Figures 1 to 14) teaches a means and method of
forming an arch structure system that overcomes problems associated with the
mechanical inadequacy of normal soil to support bridge and other structures of
interest to that, and to this, invention. The advantages associated with this
means and
method are substantial. Therefore, it would be valuable to utilize these
teachings in a
manner which also realizes the advantages associated with the retention of the
advantages associated with both precast and cast-in-place overfilled arch
structures
while reducing, or possibly eliminating, many of the disadvantages associated
with
such precast and cast-in-place structures.
While the advantages associated with the means and method this aspect of the
invention (Figures 1 to 14) are substantial, it would be extremely beneficial
if further
advantages in support could be realized.
Bending moments applied to an overfilled bridge structure are induced by the
overfill and loads, such as traffic, carried by the bridge structure. These
bending
moments must be accommodated by the bridge structure. Prior overfilled
structures
counter these bending moments by increasing structural thickness, providing
larger
amounts of steel reinforcement and/or by increasing the size and stiffness of
the arch
supports. These measures may be costly and may not be as efficient as
possible.
Therefore, there is a need for a means for efficiently minimizing bending
moments induced in an overfilled arch structure.
The technology of the first aspect of the invention (Figures 1 to 14)
significantly improves the efficiency of an overfilled bridge structure in
CA 02423228 2003-03-20
accommodating such loading over prior art structures. However, it would be
helpful
if these load accommodating efficiency advantages could be further improved.
Overfilled arch structures, in particular overfilled flat arches, are
sensitive to
outward displacement of the arch ends. This outward displacement leads to
increased
5 bending movements in the arch. Prior overf lled structures counter these
bending
moments by increasing structural thickness, providing larger amounts of steel
reinforcement andlor by increasing the size and stiffness of the arch
supports. These
measures may be costly and may not be as efficient as possible.
Therefore, there is a need for a means for efficiently reducing the outward
displacements, and particularly the sensitivity of an overfilled arch to
outward
displacements, of arch footings.
The technology disclosed and taught in the Figures 1 to 14 significantly
improves the efficiency of an overfilled bridge structure in preventing such
footing
outward displacement as compared to prior art structures. However, it would be
helpful if these resistances to arch footing outward displacement are further
improved.
The novel system disclosed with reference to Figs 1 to 14 of the present
application solves a number of the above problems by having foundation blocks
located behind or near the top of the side walls and against which the arch of
the
structure bears. The arch delivers all or at least most of its support forces
into the
foundation blocks.
This is an extremely effective system and accomplishes a number of the
objects hereof.
However, the effectiveness of this structure can be further enhanced by
improving the methods used to erect the structure. Therefore, there is a need
for a
means and a method for building the structure disclosed with reference to Figs
1 to
14 hereof.
While the cast-in-place (cip) mode of constructing an arch system is suitable
for many situations due to its economy and speed, there are certain commercial
and
technical (site) conditions for which a totally precast structure is
preferred. Some of
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these conditions are:
= time restrictions for on-site installation;
= weather conditions, especially low temperatures;
= the absence of shuttering and crew suited/trained for the cip construction
procedure;
= a need to limit the specialist contractors' duties to supplying (and,
perhaps
mounting) precast elements, in contrast to providing total contractor's
services (and
responsibility);
= limited clear space, not allowing the use of a shuttering (such as with live
train lines at the lower pathway);
= special requirements (aesthetic, etc).
Therefore, there is a need for a means and a method for building a fully
precast overfilled shallow arch structure.
The precast arch elements in many prior systems are cast on their sides. This
requires forms which have walls and also may require special handling of the
forms
to ensure proper formation of the arch elements. Still further, these elements
are
generally shipped in the side-on orientation. The elements are then lifted off
the
transporting vehicle, turned in the air to be oriented in the use orientation
(as used
herein, the use orientation is an orientation shown in Figure 32 herein as
well as in
Figures 2A to 2C, and a side-on orientation will have the elements rotated 90
with
respect to the orientation shown in these same figures). Side-on formation and
shipping has several drawbacks: complicated formwork; special transportation
problems; and lifting problems associated with lifting and turning such
elements.
Therefore, there is a need for a means and a method for forming and shipping
a precast arch element.
In the case of relatively large overfills, no connection may be required
between adjacent arch elements because the overfilled soil spreads the loads
on the
overfill surface so that no differential displacements between adjacent
elements
occur. Differential displacements are caused by loads, such as traffic loads,
placed
only on one arch element, then on the adjacent arch element, and so on. Such
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deformations may lead to so called reflection cracking (cracks that propagate
from the top
of the arch element to the pavement surface). Such deformations should be
avoided.
For shallow arch applications, shallow overfills are more frequent than high
overfills
since the shallow arch is preferably used where lost height needs to be
minimized. In such a
case, with only one or two feet or even only inches of overfill or almost zero
overfill in some
situations, the live loads may act on individual elements before being
transferred to the next
one causing the relative vertical displacements that can be such that the
pavement of the
system will be cracked due to these relative displacements.
Therefore, there is a need for a means and a method for forming an arch system
that
avoids differential displacements between adjacent arch elements of the
system.
Still further, there is a need for a means and a method for forming an arch
system in a
manner that avoids differential displacements between adjacent arch elements
of the system
even in the situation of a shallow, or even a zero, overfill.
It is desirable to provide an economical and expeditiously erected overfilled
arch
structure system and method of forming an overfilled arch structure system.
It is desirable to provide an arch structure system and method of forming an
arch
structure system that utilizes soil to create a foundation for the arch
structure.
It is further desirable to provide an arch structure and system and method of
forming
an arch structure and system that does not transfer forces associated with an
arch element
directly to walls of the arch structure and system whereby the walls are not
required to
support a significant amount of these forces.
It is also desirable to provide an overfilled arch bridge or other structure
and method
of construction therefor which enables a minimal arch curvature to be adopted.
It is further desirable to minimize the rise of the arch and hence extend the
scope of
application of the arch while still maintaining a structural arching action in
the arch of the
overfilled structure.
It is also desirable to provide an overfilled arch bridge structure and method
of
construction therefor which enables the sides/sidewalls of the overfilled
structure to be of a
lighter and therefore more economical design and faster methods of
construction as compared
to the prior art.
It is also desirable to provide an overfilled arch bridge structure which
enables such a
structure to be constructed using poor quality backfill material.
It is further desirable to provide an overfilled arch bridge structure and
method of
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construction therefor which enables the footings at the base of the overfilled
structure to be
smaller than the prior art.
It is further desirable to provide an overfilled arch bridge structure and
method of
construction therefor which enables the footings at the base of the overfilled
structure to be
omitted.
It is desirable to provide an overfilled arch bridge structure and method of
construction therefor which enables the footings at the base of the overfilled
structure to be
reduced to very small dimensions serving only for the erection of sidewalls.
It is further desirable to provide an overfilled arched bridge and method of
construction therefor which reduces dependence on large and unwieldy element
transportation and reliance on heavy erection cranes as compared to the prior
art.
It is also desirable to provide an overfilled arched bridge which is
expeditious to
produce.
It is further desirable to provide an overfilled arch structure which is
easier to handle
and transport than presently-available arch structures.
It is also desirable to provide overfilled arch structure elements which are
easier to
handle and transport than presently-available arch structure elements yet
which yield as
strong and stable structures as presently-available arch structures.
It is desirable to provide an overfilled arch structure which includes a
composite
section of precast and cast-in-place concrete.
It is desirable to provide an overfilled arch structure which includes a means
for
efficiently counteracting bending moments induced in the overfilled arch
structure.
It is desirable to provide an overfilled arch structure which includes a means
for
efficiently reducing the sensitivity of an overfilled arch to outward
displacements of arch
footings.
It is desirable to provide an overfilled arch which is prestressed to induce
moments
therein which counteract moments induced therein by overfill and loads on the
arch
structure.
It is desirable to provide an overfilled arch which has an arch end that is
customized
to induce eccentricities between an arch thrust reaction and a centerline of
the arch.
It is desirable to provide an overfilled arch has a sensitivity to outward
displacement
of arch footings that is reduced as compared to presently-available arches.
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It is desirable to provide an overfilled arch which utilizes treated soil to
create a
foundation for the arch.
It is desirable to provide an overfilled arch which includes a composite
section of
precast concrete and cast-in-place concrete and which utilizes soil to create
a foundation for
the arch, a foundation that not only reduces (vertical) settlements, but also
(horizontal)
displacements.
It is desirable to provide an overfilled arch which consists of a composite of
precast
concrete and cast-in-place concrete layers and which utilizes the technology
disclosed and
taught in the aspect of Figures 1 to 14.
It is desirable to provide an overfilled arch which uses support geometry to
automatically counteract the moments induced therein by overfill and loads on
the arch and
which utilizes the technology disclosed and taught in the aspect of Figures 1
to 14.
It is desirable to provide an overfilled arch which uses prestressing to
automatically
counteract the moments induced therein by overfill and loads on the arch and
which utilizes
the technology disclosed and taught in the aspect of Figures 1 to 14.
It is desirable to provide an overfilled arch which retains many of the
advantages
associated with precast overfilled bridge structures while eliminating, or at
least
substantially reducing, many of the disadvantages associated with a precast
overfilled
bridge structure.
It is desirable to provide an overfilled arch which retains many of the
advantages
associated with cast-in-place overfilled bridge structures while eliminating,
or at least
substantially reducing, many of the disadvantages associated with a cast-in-
place overfilled
bridge structure.
It is desirable to further improve the advantages realized by the technology
disclosed
and taught in the aspect of Figures 1 to 14.
It is desirable to provide a means and a method for building structures.
It is desirable to provide a means and a method for building a fully precast
overfilled
shallow arch structure such as disclosed in Figures 1 to 14.
It is desirable to provide a means and a method for forming, stacking and
shipping a
precast arch element such as disclosed Figures 1 to 14 in a use orientation.
CA 02423228 2008-04-21
It is desirable to provide a means and a method for forming an arch system
such
as disclosed in Figures 1 to 14 in a manner that avoids differential
displacements between
adjacent arch elements of the system.
It is desirable to provide a means and method for forming an arch system such
as
disclosed in Figures 1 to 14 in a manner that avoids differential
displacements between
adjacent arch elements of the system even in the situation of a shallow, or
even a zero,
overfill.
According to one aspect of the invention there is provided an arch support
system
comprising: A) a first selected area having side edges; B) a second selected
area spaced
above the first selected area and extending beyond a vertical projection of
side edges of
the first selected area; C) an arch structure located between the second
selected area and
the first selected area; D) the arch structure including an arch element
spanning the first
selected area, the arch element being located beneath the second selected area
and a
concrete footing element supporting the arch element; E) sidewalls independent
of the
arch structure, having a bottom end located adjacent to the first selected
area and a top
end spaced above the first selected area; F) the arch element of the arch
structure having
an end positioned adjacent to an upper end of each sidewall; and G) a
foundation block
positioned near and behind each sidewall of the arch structure, each
foundation block
supporting one of the ends of the arch element of the arch structure.
According to another aspect of the invention there is provided an arch support
system comprising: A) soil material; B) a void area defined in the soil
material; C) two
sidewalls located adjacent to the void area; D) two foundation blocks located
in the soil
material near and behind the sidewalls; E) an arch element independent from
the
sidewalls spanning the void area and having two ends; and F) one end of the
arch element
abutting each foundation block in a manner which transfers forces associated
with the
ends of the arch element to the foundation blocks.
According to another aspect of the invention there is provided an arch support
system comprising: A) soil material; B) a void area defined in the soil
material; C) a
sidewall circular in plan view and located adjacent to the void area; D) a
foundation block
located in the soil material near the sidewall; E) a dome structure
independent from the
sidewall spanning the void area and having a circumferential end; and F) the
end of the
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11
dome structure abutting the foundation block in a manner which transfers
forces
associated with the end of the dome structure to the foundation block.
According to another aspect of the invention there is provided a method of
forming an arch system comprising: A) placing elements into soil and forming
sidewalls
located at the side edges of the first selected area as defined in Claim 1; B)
constructing
foundation blocks from soil; C) locating the foundation blocks adjacent to a
selected area;
D) placing an arch structure in a position to span adjacent foundation blocks
and to rest
on the foundation blocks; and E) removing soil from between the sidewalls.
According to another aspect of the invention there is provided a method of
forming an arch system comprising: A) defining a first selected area; B)
defining a second
selected area spaced above the first selected area; C) placing two sidewalls
between the
first and second selected areas; D) using soil, forming foundation blocks near
and behind
the sidewalls; E) placing an arch structure over the sidewalls, whereby the
arch structure
consists of an arch element and concrete footings on each side; F) abutting
ends of the
arch structure against the foundation blocks; and G) transferring arch support
forces from
the arch element to the foundation blocks via small arch footings.
According to another aspect of the invention there is provided an arch support
system comprising: A) a first selected area having side edges; B) a second
selected area
spaced above the first selected area and extending beyond a vertical
projection of side
edges of the first selected area; C) an arch structure located between the
first selected area
and the second selected area; D) the arch structure including a precast arch
element
spanning the first selected area, the precast arch element being located
beneath the second
selected area and a concrete footing element between the end of the arch
element and a
foundation block; E) sidewalls independent of the arch structure, having a
bottom end
located adjacent to the first selected area and a top end spaced above the
first selected
area; F) the precast arch element of the arch structure having an end
positioned adjacent
to an upper end of each sidewall of the arch structure; and G) a foundation
block
positioned near and behind each sidewall of the arch structure, each
foundation block
supporting one of the ends of the arch element of the arch structure, the
foundation block
comprising soil.
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11a
According to another aspect of the invention there is provided an arch support
system
comprising: A) a first selected area having side edges; B) a second selected
area spaced
above the first selected area and extending beyond a vertical projection of
side edges of the
first selected area; C) an arch structure located between the first selected
area and the second
selected area; D) the arch structure consisting of a plurality of precast arch
elements
spanning the first selected area and being located adjacent to each other and
located beneath
the second selected area; E) each of the sidewalls of the arch structure
having a bottom end
located adjacent to the first selected area and a top end spaced above the
first selected area; F)
the precast arch element of the arch structure having an end positioned
adjacent to an upper
end of each sidewall of the arch structure; G) a foundation block positioned
near and behind
each sidewall of the arch structure, each foundation block supporting one of
the ends of the
arch element of the arch structure, the foundation block comprising soil; and
H) arch footings
associated with each of the precast arch elements. The precast arch elements
my be serially
spanning the first selected area and being located adjacent to each other and
located beneath
the second selected area.
According to another aspect of the invention there is provided an arch support
system
comprising: A) a first selected area having side edges; B) a second selected
area spaced
above the first selected area and extending beyond a vertical projection of
the side edges of
the first selected area; C) an arch structure located between the second
selected area and the
first selected area; D) the arch structure including a prestressed precast
arch element spanning
the first selected area, the prestressed precast arch element being located
beneath the second
selected area and a concrete footing element supporting the arch element; E)
sidewalls
independent of the arch structure, having a bottom end located adjacent to the
first selected
area and a top end spaced above the first selected area; F) the prestressed
precast arch
element of the arch structure having an end positioned adjacent to an upper
end of each
sidewall of the arch structure; and G) a foundation block positioned near and
behind each
sidewall of the arch structure, each foundation block supporting one of the
ends of the arch
structure, the foundation block comprising soil.
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llb
According to another aspect of the invention there is provided an arch support
system comprising: A) soil material; B) a void area defined in the soil
material; C) two
sidewalls located adjacent to the void area; D) two foundation blocks located
in the soil
material near and behind the . sidewalls; E) a precast arch element
independent from the
sidewalls spanning the void area and having two ends; and F) one end of the
precast arch
element abutting each foundation block in a manner which transfers forces
associated
with the ends of the precast arch element to the foundation blocks, via
concrete arch
footings.
According to another aspect of the invention there is provided a method of
forming an arch system comprising: A) placing elements into soil and forming
sidewalls;
B) constructing foundation blocks from soil; C) locating the foundation blocks
adjacent to
a selected area; D) forming an arch element in a use orientation; and E)
placing the
formed arch element in a use position which, together with the concrete
footing, spans
adjacent foundation blocks and rests on the foundation blocks, via concrete
footings.
According to another aspect of the invention there is provided a method of
forming an arch system comprising: A) defining a first selected area; B)
defining a second
selected area spaced above the first selected area; C) placing two sidewalls
between the
first and second selected areas; D) using soil, forming foundation blocks near
and behind
the sidewalls; E) forming an arch element in a use orientation; F) placing the
formed arch
element over the sidewalls; G) abutting ends of the arch element and the
concrete footing
against the foundation blocks; and H) transferring arch support forces from
the arch
element to the foundation blocks.
Some of the desired benefits or improvements mentioned above are achieved by
an arched overfilled and/or backfilled structure which includes a shallow arch
spanning
over a clear space. The sides, of the clear space are formed by sidewalls
independent of
the arch structure. Solidified zones of the backfill material or previously
existing (in situ)
ground against the footings at the springs, also referred to as ends, of the
arch and/or
behind the walls form foundation blocks which are in intimate contact with the
footings at
the arch springs in such a way that the arch delivers all of its support
forces into the
aforementioned foundation blocks, drastically reducing the normal forces,
shear forces
and bending moments in the walls and wall foundations. The arch structure
contacts the
foundation blocks in a manner that the support forces of the arch are
transferred
CA 02423228 2007-06-26
11c
to the foundation blocks and not to the sidewalls of the system. The resulting
advantages of
transferring such forces to the foundation blocks rather than to the sidewalls
will be
understood from the teaching of the present disclosure.
The arched structure system which is formed using precast concrete, or cast-in-
place
concrete, or a combination of both comprises either:
A plain concrete or reinforced concrete arch element resting on arch footings
which in turn rest on foundation blocks, the latter being a solidified portion
of the
backfill or of in situ material located outside of the wall beneath either
side of the
concrete arch. The concrete arch may be precast, cast-in-place (cip) or a
combination.
The walls can be formed using mechanically stabilized earth (MSE) or any other
type
of earth retaining wall system, including but not limited to sheet piles,
bored piles,
diaphragm walls or an excavated cip, precast or sprayed (shotcrete) concrete
wall
with or without nails/anchors; or
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12
frame comprises an arch, and the sides of the frame consist of curved or
planar walls, in which the outside surfaces of the arch and top of the walls
are
shaped such that the arch loads are directed into foundation blocks, the
latter
being solidified portions of the backfill material or in situ material,
located
s outside the frame sidewalls.
Where precast concrete is used, adjacent precast arch spans may be
structurally connected along all or part of the circumferential length.
The foundation blocks of the present invention comprise a material exhibiting
sufficient stiffness and strength such that the thrust reactions of the arch
can be
distributed via the arch footings through the foundation block to the adjacent
soil
material, such that the displacements of the arch springs are within
acceptable limits.
Shallow arches, as in the present invention, are particularly susceptible to
horizontal
outward displacements of the springs. The structure of the present invention
ensures
that the solid foundations, which are essential for such an arch, can be
provided
economically.
By enabling a load transfer from the springs of the arch via the arch footings
into the foundation blocks, the arch support forces do not need to be
transferred into
the sidewalls of the earth overfilled system. This characteristic of the
system
embodying the present invention enables the backfilling of the sidewalls to be
combined with the construction of the foundation blocks because all or part of
the
solidified backfill of the sidewalls or the solidified in situ ground directly
constitutes
the arch foundation blocks. This also enables more efficient construction
procedures
to be adopted for construction of the walls, which can be made considerably
lighter
than prior art systems.
Furthermore, by enabling direct transfer of the arch support forces into the
foundation blocks at the top of the sidewalls, it is possible to adopt a
flatter arch than
is possible and economic for the conventional state of the art. This is
because the
loads and bending moments transferred into the sidewalls of a conventional
overfilled arch are significantly larger for a flatter arch than for a higher
(less flat)
arch. A flatter arch (smaller arch rise) has the advantage that for a given
clearance
CA 02423228 2003-03-20
13
beneath the sides of the arch, the lost height (see lost height LH 1 and LH2
in Figures
1A and 1B) can be reduced, and the distance between the lower and upper paths
of
the overfilled arch system can be reduced, thereby increasing the scope of
arch
structure application. Thus, the total lost height LH 1 or LH2 will be
considerably
reduced from those values indicated in Figures 1 A and 1 B.
The present invention also includes a cover-and-cut method of such a system.
While a bridge system is discussed herein, it is to be understood that the
present invention can be applied to other systems as well without departing
from the
scope of the present disclosure and invention. For example, any type of
underground
space (including, but not limited to, shelters, warehouses, storage spaces,
backf lled
and overfilled, or only backfilled or built into existing in situ ground) can
be within
the scope of the present invention and disclosure and it is intended that the
present
invention as defined by the teaching of this disclosure and the claims
associated
therewith will cover such structures as well.
Is Other objects are achieved by an overfilled bridge arch that includes both
precast and cast-in-place layers. The overfilled bridge arch can also be
prestressed in
an efficient and effective manner, or the ends of the arch arranged in such a
way,
such that bending moments induced by loading are efficiently and effectively
accommodated and sensitivity of the arch to arch footing outward displacement
is
also reduced.
The overfilled arch bridge structure embodied in the aspect of Figures 15 to
31 of the present invention can be used in conjunction with the technology
disclosed
and taught in the aspect of Figures 1 to 14 hereof to thereby realize
additional
advantages for each technology.
The composite overfilled bridge structure embodied in the aspect of Figures
15 to 31 of the present invention thus realizes advantages for both precast
and cast-
in-place structures as well as reducing, or even eliminating, many
disadvantages
associated with such precast and cast-in-place arches. Additional advantages
are also
realized due to the composite nature of the structure of the present
invention,
including the ability to efficiently waterproof the structure as well as to
include
CA 02423228 2003-03-20
14
efficient joint seals.
The overfilled bridge and elements thereof embodying Figures 15 to 31 of the
present invention make an overfilled bridge efficient to transport, handle and
erect,
yet will produce a stable and efficiently waterproofed structure.
Further objects are achieved by a means and method (Figures 32 to 51) for
forming an arch system such as disclosed in Figures 1 to 14 in which the arch
elements are fully precast in a use orientation, then stacked and shipped in a
use
orientation. It is noted that the term "fully precast" is used herein to mean
that the
arch element is fully precast and with the exception of some cast-in-place
concrete in
the footings and in some cases cast-in-place concrete in the crown joints. The
arch
elements are placed on the foundation blocks in a manner which distributes
forces
associated with the arch elements to the foundation blocks, as taught in the
disclosure of the aspect of Figures 1 to 14.
The form work is very simple and no counter forms are usually required.
Furthermore, there is no need to turn the elements in the air while hanging
from a
crane.
The arch elements can be pre-stressed by pre-deformation either during
movement from the shipping vehicle to the in place location, or in another
manner.
The pre-stressing will partly or wholly compensate for the influence of
possible
outward yield (deformation) of the abutments (foundation blocks). The elements
are
placed in their pre-deformed shape and come back to their intended and optimal
shape when overfilled.
The width of arch elements may be limited by the geometric transportation
limitations and the weight. The lying down or use orientation has several
advantages
over the standing way or the side on orientation including the advantages
associated
with longer elements. For the shallow arches of the present invention, longer
elements can be transported (even with footings attached) than with other arch
geometries.
It is noted that the means and method disclosed herein (e.g. Figures 32 to 51)
can be applied to skew arch structures as well as to spans which do not allow
one
CA 02423228 2003-03-20
element solutions but which require a crown joint to connect two halves
together.
Therefore, spans can range from about twelve feet to eighty-four feet or more.
The invention may be carried out in various ways and a number of preferred
examples of embodiments will now be described with reference to the
accompanying
5 drawings, in which:
Figures 1 A and 1 B illustrate cross sectional views of prior art systems.
Figure 1 C illustrates forces associated with overfilled arches, as
characteristic
of a prior art system.
Figure 2 shows the typical cross section for the basic embodiment of the
10 present invention using a flat arch resting on foundation blocks.
Figure 3 shows the typical cross section for the basic embodiment of the
present invention using a continuous frame supported by foundation blocks in
which
the arch and the sidewalls are integral and continuous, the embodiment shown
includes a stepped outer surface.
1s Figure 4 shows the typical cross section for the basic embodiment of the
present invention using a continuous frame supported by foundation blocks in
which
the arch and the sidewalls are integral and continuous, the embodiment shown
includes a protruding corner.
Figure 5 is a flow chart for a cover-and-cut method embodying the present
invention.
Figure 6 shows a system produced by a cover-and-cut method.
Figure 7 is a flow chart showing the overall method of forming an arch
support system embodying the present invention.
Figure 8 is a top plan view of an alternative form of the present invention in
which the overall system includes a dome and an arcuate sidewall.
Figure 9 illustrates a multi-arch section bridge form of the present
invention.
Figure 10 illustrates the present invention as embodied in a skewed arch
bridge.
Figure 11 illustrates the present invention incorporating a battered slope at
the
ends of the structure to conform with a battered (sloped) fill embankment.
CA 02423228 2003-03-20
16
Figure 12 illustrates a method step included in the method embodying the
present invention in which an arch structure is prestressed.
Figure 13 illustrates a method of forming several different arch spans using
the same mould or formwork, by blocking off the mold or formwork.
Figure 14 illustrates a method of forming several different arch spans using
the same mould or formwork by connecting extensions to the mould or formwork.
Figure 15 shows a basic overfilled bridge structure as disclosed in Figures 1
to 14.
Figure 16 is an elevational view of a composite overfilled bridge structure
embodying the present invention.
Figure 17 is a view taken along line A-A of Figure 16.
Figure 18 shows detail B of Figure 17.
Figure 19 is an elevational view of an overfilled arched bridge structure of
the
present invention illustrating arch footing elements.
Figure 20 is a detail view of one form of a bearing forming an arch spring to
arch footing interface.
Figure 21 shows a concentric support reaction of the prior art.
Figure 22 is a diagram illustrating moment distribution in an arch for a
conventional arch support such as shown in Figure 21.
Figure 23 shows an eccentric arch support reaction according to the teaching
of the present invention.
Figure 24 is a diagram illustrating the moment induced by support reaction
eccentricity.
Figure 25 is a diagram illustrating the resultant moment distribution for a
customized end geometry such as shown in Figure 23.
Figure 26 is a diagram illustrating moment optimization obtained by
prestressing an arch.
Figure 27 is a diagram illustrating moment distribution in an arch for a prior
art arch support.
Figure 28 is a diagram illustrating moment induced by prestressing load
CA 02423228 2003-03-20
17
placed on an arch.
Figure 29 is a diagram illustrating a resultant moment distribution for a
prestressed arch.
Figure 30 is a detail view from Figure 19 of.a bearing interposed between an
arch spring and an arch footing in which the arch will be prestressed.
Figure 31 is a diagram illustrating use of a tie in order to prestress the
arch.
Figure 32 is an elevational view of a completed arch structure as disclosed in
Figures 1 to 14 and which is formed in accordance with the teaching of the
present
disclosure.
Figure 33a is a plan view of a system with skew alignment that can be formed
in accordance with the teaching of the present disclosure.
Figure 33b is a plan view of a system with curved alignment which can be
formed in accordance with the teaching of the present disclosure.
Figure 33C is a plan view of a system with an irregular alignment which can
is be formed in accordance with the teaching of the present disclosure.
Figure 34a is a plan view of a curved system which can be formed in
accordance with the teaching of the present disclosure showing adjacent arch
elements.
Figure 34b is a plan view of a skewed system which can be formed in
accordance with the teaching of the present disclosure showing adjacent arch
elements.
Figure 34c is a plan view of a conventional span system which can be formed
in accordance with the teaching of the present disclosure showing adjacent
arch
elements.
Figure 35 is a plan view of a form used to form arch elements in a use
orientation in accordance with the teaching of the present disclosure.
Figure 36 is an end elevational view of the form shown in Figure 35.
Figure 37a shows an arch element that has been formed in the use orientation
being moved in the use orientation.
Figure 37b shows a top plan view of the arch element being moved in the use
CA 02423228 2003-03-20
18
orientation.
Figure 38 shows an arch element having a prestressing element associated
therewith.
Figure 39 shows a portion of an arch element in which bores are defined to
accommodate tie elements, such as dowel rods or the like.
Figures 40 and 40a show a tie element located in a bore of the arch element.
Figure 41 is a longitudinal section of a plurality of adjacent arch elements.
Figure 42 shows a detail of a connection between adjacent arch elements.
Figure 43 is an elevational view in section of a completed arch system in
which adjacent arch elements are connected together in accordance with the
teaching
of the present disclosure.
Figure 44 is a detail view showing a connection between two adjacent arch
elements of a completed arch system in accordance with the teaching of the
present
disclosure.
Figure 45 is a detail view showing an alternative form of a connection
between two adjacent arch elements in accordance with the teaching of the
present
disclosure.
Figure 46 is an elevational view in section of an arch system showing the arch
system during one step in the process of erecting the system in accordance
with the
teaching of the present disclosure.
Figure 47 is a detail view of an end of an arch element and a portion of a
foundation block during one step in the process of erecting the arch system in
accordance with the teaching of the present disclosure.
Figure 48 is a detail view of an end of an arch element and a portion of a
foundation block during one step in the process of erecting the arch system in
accordance with the teaching of the present disclosure.
Figure 49 shows a detail view of one form of an arch element and its footing
that is included in the disclosure of the present invention.
Figure 50 shows another detail view of a form of an arch element and its
footing that is included in the disclosure of the present invention.
CA 02423228 2003-03-20
19
Figure 51 shows another detail view of a form of the arch element and its
footing that is included in the disclosure of the present invention.
Other objects, features and advantages of the invention will become apparent
from a consideration of the following detailed description and the
accompanying
drawings.
FIRST ASPECT
Dealing with a first aspect of the invention discussed now with reference to
Figures 1 to 14, as will be understood from the teaching of the present
disclosure,
instead of one footing (which may be in reinforced concrete) that distributes
the
horizontal and vertical support forces, the system embodying the present
invention
includes a small arch footing at the springs of the arch plus a large
foundation block
on which the arch footing rests. Thus, the stresses on the soil (ground) are
distributed
in two stages, which is more effective and less expensive than prior art
systems. The
foundation block of the present invention, while large in volume, is still
relatively
inexpensive because the backfill needs to be well compacted anyway, the
present
invention merely adds stabilizing materials. The present invention can use
poor
material which otherwise may be unsuitable for backfilling a normal bridge, by
making it suitable through adding stabilizing materials, thus creating a
foundation
block. The arch of the present system contacts the thus-formed foundation
blocks via
the arch footings, in a manner to transfer all or at least most of the arch
support
forces to the foundation block. In practice, this reduces or eliminates the
forces
applied to the sidewall and to the wall footings thereby resulting in
concomitant
advantages. In most cases, the sidewalls are connected to the foundation
blocks and
are therefore held in place by the foundation block or blocks. The large
dimensions
of the foundation block together with its weight allows such an advantageous
force/stress distribution, with outward (horizontal) movements/displacements
of the
arch ends (springs) being minimized in a very economical manner, even where
relatively soft soil exits beneath the foundation block. This feature of the
invention is
especially advantageous for a relatively flat arch. Flat arches are used in
conjunction
with wide clearances with a minimum of lost height LH (Figures IA, 1B and 2).
CA 02423228 2003-03-20
Referring to Figure 2, it can be understood that top-arch arched overfilled
andJor backfilled structure 10, which also will be referred to as an arch
structure, and
method of construction embodying the present invention includes an arch span
12,
which also will be referred to as an arch element, or simply an arch, which
forms the
5 roof of a void 14 within an earth filled space. Beneath arch span 12, walls
16 and 18,
which will also be referred to as side walls or retaining walls, retain
backfilled earth
20 or excavation edges 22 and 24 of previously existing (in situ) ground
material on
either side of open space 14. The arch and retaining walls may or may not be
structurally connected. The art and practice of the present invention enables
the arch
10 and the walls to be constructed independently, in different construction
phases. The
purpose and form of the arch, the retaining walls and the means of founding
these
two key components of the backfilled andlor overfilled structure will be
understood
from the teaching of the present disclosure.
Structure 10 can be located between first selected area 30 which can be the
15 floor of a void or a lower pathway, and which includes a plane 32, and a
second
selected area 34 which can be a roof of a void or an upper pathway which
includes a
plane 36.
The arch span comprises reinforced or unreinforced concrete, which may be
manufactured as precast elements or cast in place or a combination of these
means.
20 The arch span is founded via arch footings and foundation blocks 40 and 42
on general earth backfill 20 and/or on in situ soil (the surface of the
previously
existing (in situ) subsoil having been excavated to that extent). Foundation
blocks 40
and 42 are each placed behind corresponding sidewalls 16 and 18 respectively
of the
overfilled and/or backfilled arch structure during its construction. Arch
footings 48
and 50, formed of concrete or reinforced concrete are interposed between
springs 44
and 46 which will also be referred to as ends of arch span 12 and the
foundation
blocks to further distribute forces over a wide area as indicated by arrows 54
thus
also reducing the strength and stiffness requirements of the solidified fill
material.
As can be understood from the figures, especially Figure 2, forces 54 are
radially
directed forces associated with the springs of the arch span. As can be
understood
CA 02423228 2003-03-20
21
from Figure 2, the contact between the springs of arch span 12 and the
foundation
blocks is arranged so that forces associated with the springs of the arch are
transferred via the arch footings to the foundation blocks. Accordingly, the
sidewalls
do not support the arch structure in any significant manner, at least not in
the
horizontal direction. In fact, as shown in Figure 2, since the springs of arch
span 12
are spaced apart from the top ends 55 of the sidewalls, it can be stated that
all or at
least most of the forces associated with the springs of the arch span are
transferred to
the foundation blocks. The foundation blocks comprise a solidified material
exhibiting sufficient stiffness and strength such that the thrust reactions of
the arch
can be distributed through the foundation block to the adjacent soil material.
Thus
the system embodying the present invention enables three objectives to be
achieved
with one structural member because the foundation blocks serve both to secure
the
sidewalls of the structure while at the same time to provide the foundation
for the
arch structure and to constitute all or part of the backfill.
As indicated by arrows 56 in Figure 2, the foundation blocks distribute the
concentrated arch support forces at the springs of the arch via arch footings
onto a
sufficiently large earth backfill area such that the bearing pressure on the
volume of
earth to which the arch loads are applied does not cause unacceptable
displacements,
especially in the horizontal direction. Materials which may be used for
creation of
the foundation blocks 40 and 42 include cement stabilized earth (soil cement),
lime
stabilized earth, hardened flowable fill, lightweight hardened flowable fill,
jet
grouted earth or other such manufactured or treated material. These materials
have a
strength and stiffness superior to that of normal earth, but considerably less
than that
of standard concrete. Thus, foundation blocks 40 and 42 are much more
economical
to produce than standard concrete. Quite often, earth material not suitable
for bridge
backfilling can be used for the foundation blocks since it is treated with
cement and
or lime or other additions. Additionally, material that would need to be
deposited in
special dumps, since they are environmentally critical, may be used as
backfill
because when treated with cement, etc, some such materials are no longer
critical or
dangerous.
CA 02423228 2003-03-20
22
Walls 16 and 18 may be constructed independently of, and before, arch 12
and can be designed primarily for the purpose of retaining the backfill soil
placed at
the outside of the backfilled structure; or as a continuation of the concrete
arch span
so as to be one-piece and monolithic therewith as indicated by system 10'
shown in
Figure 3 or system 10" shown in Figure 4.
Independently constructed sidewalls may comprise mechanically stabilized
earth (MSE) using precast wall panels or any other type of earth retaining
wall,
including but not limited to sheet piles, bored piles or an excavated cast-in-
place
(cip), precast or sprayed (shotcrete) concrete wall with or without
nails/anchors. The
independence of sidewall and arch construction enables the construction
process to
be staged as independent activities i.e. construction of the sidewalls and
solidified
backfill, and subsequent placement of the arch and overfill of the structure.
Since all or at least most of the arch support forces are directed onto the
foundation blocks, wall foundations 57 and 58 respectively can be designed to
be
very small as compared to wall foundations F 1 and F2, or omitted completely.
As can be understood by comparing Figures 1C and 2, the system embodying
the present invention has several advantages over prior art systems. By
locating the
foundation blocks behind the wall or walls a number of advantages become
associated with the system embodying the present invention.
Normal foundations below the walls, which usually require significant cuts
into the ground and which can be expensive and environmentally disadvantageous
especially in the case of river beds (wetlands act prohibits the interference
with river
beds) or when deposited wastes have to be removed prior to foundation
construction,
can be significantly reduced.
Since the foundation blocks of the present system are located behind the
sidewalls, they are less at risk when scour problems are present, than the
footings of
prior art systems.
The foundation blocks of the present invention are simpler, cheaper and can
be faster to build than prior art footings. An additional advantage is that
general
earthworks machinery may be used for their construction rather than specialist
CA 02423228 2003-03-20
23
equipment used for placing concrete.
Earth material unsuitable for backfill in prior art systems can be made
suitable
for the system of the present invention even for the solidified backfill zones
(foundation blocks), by using cement, lime or other solidifying materials
and/or
treatment.
The foundation blocks are unreinforced (except by anchors, mostly synthetic
anchors in some forms of the invention) and therefore are more durable and
long-
lasting compared to prior art systems. In the case of cement or lime
treatments, the
foundation blocks actually become harder over time; they cannot deteriorate.
Because the system of the present invention primarily uses earth material
available at the site, the system of the present invention has several
ecological
advantages, including less transportation (less air pollution), and less
exploitation of
valuable gravel resources. There is even the possibility of backfilling the
wall with
environmentally hazardous materials which in some cases become harmless when
1s mixed with cement, lime or other additive.
Furthermore, by comparing the system shown in Figure 2 to the system
shown in Figure 1 B, it can be understood that the system embodying the
present
invention has an advantageously reduced lost height LH required to achieve the
same
clearance profile as compared to prior art systems.
There are many alternative forms of the present invention. One form of the
invention is the case where the upper pathway plane 36 (in Figure 2) coincides
with
the top surface of the arch span 12, thus omitting the earth overfill which is
a normal
characteristic of the present art. As mentioned above, two forms of the
invention are
shown in Figures 3 and 4 as systems 10' and 10" respectively. The flat arch
form of
the invention may rest on foundation blocks which simultaneously serve to
support
the sidewalls, or may comprise a continuous frame supported laterally by
foundation
blocks as shown in Figures 3 and 4. Figure 3 shows system 10' which includes
steps
60 in the upper sides of the arch structure 12' as well as elements 62, such
as pipes or
the like, which are used to grout the contact zone between the structure
itself and the
foundation block, thereby additionally securing the intimate contact and force
CA 02423228 2003-03-20
24
transfer from the arch structure 12' of system 10' to foundation blocks 40'
and 42'.
Forces from arch structure 12' are distributed to the foundation blocks as
above
described and as identified by arrows 63. Figure 4 shows an embodiment 10" of
the
flat arch using a continuous one-piece monolithic frame whereby protruding
corner
64 is used (instead of the stepped upper side of the arch structure 12' to
ensure the
force transfer from the structure to the foundation block. In order to ensure
a secure
connection between arch structure 12" and foundation blocks 40" and 42", a
channel
65 can be defined through each protruding corner. Cement or concrete or the
like can
be placed through channel 65 and/or pipes can be used as in the other
embodiments
of the invention to improve the intimacy of the contact between protruding
corner 64
and foundation blocks 40" and 42".
Also, as shown in Figures 2 and 3, the sidewalls of the system of the present
invention can be planar and extend perpendicularly with respect to plane 32
contained in first selected area 30 or can be inclined at an oblique angle 0
with
respect to plane 32 with angle 0 being an acute angle whereby the sidewalls
incline
toward each other. Furthermore, as indicated in Figure 4, the sidewalls can be
curved
in the manner indicated at area 68 with respect to a plane 69 which is upright
with
respect to plane 32. In some cases, plane 69 can be perpendicular to plane 32.
In
other cases, as will be discussed below, the curved nature of the sidewall
will make
that sidewall cylindrical in nature.
Furthermore, any or all of the systems of the present invention can include
reinforcing elements RE in either or both the arch and/or the sidewalls as
indicated in
Figures 2 and 4. The foundation block as such is unreinforced with the
exception of
the mostly synthetic anchors used to tie the MSE (mechanically stabilized
earth)
walls back into the backfill (for the case where this type of wall is used).
The system of the present invention can also be used in conjunction with a
cover-and-cut technique. As indicated in Figure 5, a cover-and-cut method
embodying the present invention includes forming sidewalls by the use of
sheet,
soldier, driven or bored piles, diaphragm walls or other similar materials in
step 70;
constructing foundation blocks from soil in step 72; creating the foundation
blocks
CA 02423228 2003-03-20
adjacent to a selected area in step 74; placing an arch element in a position
to span
adjacent foundation blocks and to rest on the foundation blocks in step 76;
covering
the arch element with soil in step 78 (if soil cover is required); and
removing soil
from between the sidewalls in step 80. The final product of such a method is
shown
5 in Figure 6 as system 90. System 90 includes sidewalls 92 and 94 which have
been
first constructed using sheet, soldier, driven or bored piles, diaphragm
walls, etc.,
subsequently foundation blocks 96 and 98 are constructed by manufacturing soil
cement with the excavated material or by shallow soil mixing techniques where
possible or by other means of solidification; next, shallow arch span 100 is
placed or
to constructed, and in the final step the arch is covered to natural grade 104
and the soil
material 102 located between the sidewalls is removed. Where permissible, the
"cover-and-cut" method can be used without first placing the sidewalls if the
excavation walls can be secured using shotcrete and/or nails and anchors
subsequent
to and/or during removal of the material beneath the flat arch. It is noted
that
15 foundation blocks 96 and 98 can be created by excavating and replacing
material
with soil cement or the like, or by using a solidification process from the
top such as
"shallow soil mixing" or grouting or other manner to solidify the material. It
is also
noted that sidewalls 92 and 94 can include sheet piles, or soldier piles, or
driven piles
or bored piles or diaphragm walls or excavation protected by shotcrete and
20 nails/anchors or any other practical means of creating a retaining wall
appropriate for
this application. As shown in Figure 6, springs 106 and 108 of arch span 100
bear via
arch footings on the foundation blocks.
As indicated in Figure 7, the present invention includes a method of forming
an arch system which comprises defining a first selected area in step 120;
defining a
25 second selected area spaced above the first selected area in step 122;
placing two
sidewalls (vertical, upright or inclined) between the first and second
selected areas in
step 124; forming foundation blocks near the sidewalls in step 126; placing an
arch
span over the sidewalls in step 128; abutting ends of the arch span against
the
foundation blocks in step 130 (via arch footings); and transferring arch
structure
support forces from the arch span to the foundation blocks in step 132. The
method
CA 02423228 2003-03-20
26
can further include a step 134 of spacing the arch span apart from the
sidewalls. The
method can further include a step 136 of providing soil material near the
sidewalls
and the step of forming foundation blocks includes stabilizing the soil
material. The
step of stabilizing the soil material can also include solidifying the soil
material in
step 13 8. The method can further include inclining the sidewalls toward each
other in
step 140, and further include spreading the forces between the arch structure
and the
foundation blocks over an area larger than the ends of the arch span in step
142. As
indicated in step 144, the step of placing two sidewalls can include casting
the
sidewalls in place, or as shown as step 146, the step of placing an arch span
can
include casting the arch span in place. The step of placing two sidewalls can
include
precasting the sidewalls in step 148, and the step of placing an arch span can
include
precasting the arch span in step 150. The method defined can further include
reinforcing the arch span in step 152, and can further include reinforcing the
sidewalls in step 154.
The above disclosure has been directed to a straight bridge structure;
however, the above-disclosed means and methods can be applied to curved or
angular shapes in plan view or in longitudinal section as well without
departing from
the scope of the present disclosure.
As discussed above, the present invention can also be embodied in a domed
structure. As shown in plan view in Figure 8, a system 10" ` includes a dome
160
which corresponds to arch 12 and which spans a void area therebeneath. An
arcuate
sidewall, which can be circular or elliptical in plan view (cylindrical) or
the like
identified as sidewall 161 is located beneath dome 160. A dome footing and
foundation block 162 are located to abuttingly engage the spring 164 of dome
160 in
the manner described above. Since the only difference between system 10" ` and
system 10 is the dome shape of system 10" `, no further discussion of system
10" `
will be presented. It is also noted that while a spherical dome shape has been
discussed, those skilled in the art will understand that the arcuate shape of
the
present invention can also be other arcuate shapes as well, including
elliptical or
other such arcuate shape. Such arcuate shapes are intended to be included in
the
CA 02423228 2006-03-08
27
scope of the present disclosure as well.
The dome embodiment of the present invention has an advantage that the
solidified
backfill (foundation block) avoids the need for circumferential tie rods (at
the spring level
of the dome) because of the rigidity of the foundation block.
It is also noted that the scope of the present disclosure also includes not
solely
bridges with pathways on top and under it, but also any kind of underground
space, with
one or several openings for access, exit, etc.
Still further, the system embodying the present invention can be used in
connection
with other forms of bridges as well, such as a multi-arch structure 200 shown
in Figure 9, a
skewed arch structure 300 shown in Figure 10 and disclosed in US Patent Number
6,434,892, issued on August 20, 2002, by the same inventor and titled
"Overfilled, Precast
Skewed Arch Bridge," or an arch structure 400 shown in Figure 11 with battered
ends
whereby the ends of the arch structure are sloped to match the gradient of the
sides of the
overfill embankment through with the arch structure passes. It is noted that
systems 200,
300 and 400 all have arches, such as arches 202, 302 and 402 which abuttingly
engage
foundation blocks 204, 304 and 404 respectively in the manner discussed above.
In the case
of the multi-arch system, foundation blocks can replace the sidewalls that
would otherwise
be interposed between adjacent arch sections, such as indicated by foundation
blocks 206.
Foundation blocks 304 and 404 may be extended beyond the length of the arch
elements
302 and 402. As shown in Figure 10, skewed bridge 300 has a skew angle a, with
angle
a<90 . The methods of the present invention can be modified to include the
above-
mentioned arch system forms. These modifications are indicated in Figure 7 as
defining a
skewed arch system in step 700 and defining an arch system with battered ends
in step 800.
Reference is made to US patent no. 6,434,892 for such steps.
It is noted that the contact between the arch structures and the foundation
blocks in
systems 200, 300 and 400 is identical to the contact between the arch
structures and the
foundation blocks discussed above. Accordingly, such contact will
CA 02423228 2003-03-20
28
not be discussed in detail, but reference is directed to the above discussion.
Furthermore, as indicated in Figure 12, flat (shallow) arches 12A are
susceptible to outward displacement 12A' of their springs/ abutments.
Therefore, the
present invention contemplates prestressing the arch by pressing (jacking) the
arch
on one side and thus producing the opposite of what would happen if there were
an
outward displacement. This prestressing is indicated in Figure 12 by arrow
12A".
The susceptibility to outward displacement, by this token, is considerably
reduced.
Accordingly, the method of the present invention can further include a step
900 of
prestressing the arch structure.
As illustrated in Figures 13 and 14, one of the variants of the present
invention is that arch section 12D can be circular (of constant radius of
curvature).
Such an alternative has several advantages, including the ability to be
precast in
which case a single mould can be used both to form large span arches, and by
blocking off part of the mould, to form smaller arch spans as indicated in
Figure 13
at areas 12B; or cast in place, in which case formwork 12F can be extended as
indicated at 12FE with a circular arch shape as indicated in Figure 14 by
extension
12FE on basic formwork 12F. The method embodying the present invention can be
modified to include this step as well and is indicated in Figure 7 by step 950
of using
a common mould to create more than one form of the arch structure.
SECOND ASPECT
Broadly dealing now with a second aspect of the invention discussed with
reference to Figures 15 to 31 which have their own reference number sequence
for
the figures which overlaps with the sequence for Figures 1 to 14, the
overfilled arch
bridge structure and the elements thereof embodying the present invention can
be
independently used or used in conjunction with the overfilled bridge disclosed
in
Figures 1 to 14. While the present aspect will be disclosed in combination
with that
structure, it should be understood that the present aspect can be used
independently
of such structure and no limitation is intended by the disclosure of this
invention in
combination with the invention disclosed in the aspect of Figures 1 to 14. The
basic
structure disclosed in the first aspect is shown in Figure 15 as structure 10.
As
CA 02423228 2003-03-20
29
disclosed in the aspect of Figures 1 to 14, earth overfilled arched structure
10
includes a shallow arch 12, which is concrete in Figures 1 to 14, spanning a
clear
space 14. Sides of the clear space are formed by curved or straight walls,
such as
wall 16, and solidified zones of earth material (backfill or in situ) bear
against the
springs of the arch and/or behind the walls and form foundation blocks, such
as
foundation block 18 which are in intimate contact via arch footings, such as
footing
20, and with the springs of the arch and/or with the upper part of the
sidewalls in
such a way that the arched structure delivers most or all of its support
forces into the
foundation blocks. These, due to their size and weight, transfer and spread
the
support forces to the subsoil, such as subsoil 22, which can be backfill
and/or in situ
material, so that displacements, especially in the horizontal directions, are
minimal.
Overfill, such as earth overfill 24 is placed on top of arch 12. The
disclosure of this
structure will not be further presented with reference to Figures 15 to 31,
with
reference to the aspect of Figures 1 to 14 made for such disclosure.
As discussed above, the overfilled bridge structure embodying the present
invention combines precast and cast-in-place advantages and also stabilizes
the arch
structure.
Referring first to Figures 16-18, it can be seen that the present invention is
embodied in an overfilled bridge structure 28 comprising an arch 30 which has
a
lower layer 32 which is precast and an upper layer 34 which is cast-in-place.
As
shown in Figure 15, the arch layers contact footings, such as footing 18, at
arch ends,
such as arch end 20, when used in conjunction with the structure disclosed
Figures 1
to 14. Precast elements form the initial arch shape and cast-in-place concrete
is
poured over the precast elements to complete an overfilled arch of a shape and
thickness that is similar to the shape and thickness of prior structures.
As can be understood from Figures 16, 17, and 18, layers 32 and 34 can be
reinforced concrete with longitudinal rebars, such as rebar 36, and arch
rebars, such
as rebar 38, therein. Joint seals, such as joint seal 40, can be included as
well and a
waterproofing, such as waterproofing 42, can also be included between layers
32 and
34. Shrinkage crack inducers, such as shrinkage crack inducer 46, can also be
CA 02423228 2003-03-20
included in cast-in-place layer 34 to induce shrinkage cracks, such as
shrinkage
crack 44, within the cast-in-place concrete, adjacent to the gaps between
precast
elements. As can be seen in Figure 18, the thickness of the cast-in-place
layer 34
may be locally increased adjacent to the gaps between precast elements, in
order to
5 increase the depth of the concrete section at this location. This has the
inherent
advantage of increasing the longitudinal moment carrying capacity of these
locations, thereby maintaining the longitudinal load-sharing advantage of the
cast-in-
place previous art.
The precast layer of the arch forms the complete arc of the arch span, but is
10 thinner, and therefore lighter to transport and handle than prior art
precast arches.
The precast arch elements are sized to be able to support their own self-
weight
during transportation and placement, as well as to be sufficiently strong to
enable
casting layer 34 of cast-in-place concrete over the precast layer 32. Those
skilled in
the art will understand how to size and form precast layer 32 based on the
teaching
15 of this disclosure. The composite section of precast and cast-in-place
concrete thus
formed has the thickness and strength of previous structures which are
exclusively
precast or exclusively cast-in-place arches.
The main advantages of the composite arch system embodying the present
aspect of Figures 15 to 31 include: the weight of the transported elements is
lower,
20 and can be lower by half, than prior precast elements (or alternatively the
elements
can be made wider such that fewer elements need to be transported); and the
cast-in-
place layer 34 facilitates load sharing longitudinally along the arch to
distribute
concentrated loads. Furthermore, placement of waterproofing between precast
elements is better facilitated than in prior structures. Thus, the composite
system
25 embodying the second aspect hereof has advantages over either a fully
precast arch.
No formwork or formwork support structure is required to form the arch
embodying
the second aspect of Figures 15 to 31. The elimination of formwork or formwork
support structures will result in considerable saving in costs associated with
the
formwork, and the clearance below the arch will not be reduced during
construction
30 since a temporary support structure is not required. Thus, the structure
embodying
CA 02423228 2003-03-20
31
the aspect of Figures 15 to 31 of the present invention also has advantages
over cast-
in-place arches.
As also mentioned above, the overfilled bridge structure of the present
invention includes means for reducing the bending moments within the
overfilled
arches, as well as reduces the arch's sensitivity to any outward displacement
of the
arch footings. Reducing the bending moments also reduces the structural depth
and
steel reinforcement required with the advantages concomitant to such
reduction.
Broadly, the means include either customized arch end geometry or
prestressed arches, with the prestressing occurring either prior to or during
loading.
Referring to Figures 19 and 20, a basic arch footing 50 of a concrete arch CA
is shown as including a cast-in-place arch footing 52 located between arch CA
and
wall 16 and foundation block 18. A bearing 54 is interposed between the arch
spring
and the arch footing. Overfill 24 is positioned above the arch CA.
The structure embodying the second aspect of the present invention (Figures
15 to 31) improves over the basic arch footing shown in Figures 19 and 20. The
structure of the Figures 15 to 31 of the present invention includes two main
means
by which the bending moments and thus the structural depth and steel
reinforcement
are reduced. The means embodying Figures 15 to 31 of the present invention
include
a customized arch end geometry (Figures 23, 24 and 25) and prestressing the
arch
prior to or during loading (Figures 26, and 27-31).
Referring to Figures 21 and 22, a prior art arch support PS is shown in
conjunction with an arch C having a centerline CL. As shown in Figure 21, arch
support PS is located to provide arch support reaction at centerline CL. The
resulting
moment distribution is indicated in Figure 22 by dotted line IM and in which
negative bending moments NM are defined adjacent to the shoulders of the arch
and
a positive (sagging) bending moment BM1 is defined at the crown of the arch.
The means embodying the aspect of Figures 15 to 31 of the present invention
is illustrated in Figure 23 includes an eccentric arch support 60. As shown in
Figure
23, eccentric arch support 60 is located to create arch support reaction 62
spaced
apart from centerline CL of arch C, with the eccentricity being indicated in
Figure 23
CA 02423228 2003-03-20
32
by reference number 64. The moment induced by support reaction eccentricity is
indicated in dotted line HM shown in Figure 22. As can be understood from
Figure
22, the reaction due to the reaction eccentricity induces a constant negative
"hogging" moment BM2 in the arch.
Referring next to Figure 23, it can be understood that adding the constant
negative moment BM2 to the negative/positive moment shown in Figure 22 for
moment distribution in the arch yields a resultant moment distribution RM
shown as
a dotted line in Figure 25.=As can be understood from Figure 25, resultant
moment
distribution RM has increased negative bending moments RMN located near the
shoulders and a decreased positive (sagging) bending moment SM near the crown.
Bending moment SM is a moment addition of bending moments BM 1+ BM2, with
the total of (BMl + BM2) being less than BM1 due to the signs of the bending
moments. This can also be visualized using the absolute value of the total of
(BM 1+
BM2). Thus, the peak positive moments in the arch crown are reduced over the
prior
art (non-eccentric) form of arch support.
Prestressing can also be used to reduce the bending moments within an earth
overfilled arch. Prestressing is illustrated in Figures 26-31. As shown in
Figure 27,
loading L on an arch will induce a bending moment IM' which, as discussed in
relation to Figure 22, includes negative bending moments NM' at the shoulders
and a
positive (sagging) bending moment BM 1' at the crown. Figure 27 is similar to
Figure
22, but is included here to better explain the prestressing embodiment of the
aspect
of Figures 15 to 31 of the present invention.
As shown in Figure 26, prestressing loads PL are applied to an arch to
displace the arch by a distance DPL prior to or during loading of the arch.
Figure 28
illustrates the moment IMS induced in the arch as a result of prestressing
load PL. As
shown in Figure 28, induced bending moment IMS is a variable negative
"hogging"
moment which has a negative portion BM2' near the crown of the arch. During
prestressing, a (hogging) moment is induced and then is locked into the arch.
This
moment is opposite to the peak (sagging) moment in the crown of a
conventionally
supported arch.
CA 02423228 2003-03-20
33
Figure 29 illustrates the arch bending moment RMM which results by adding
bending moment IMS associated with prestressing to bending moment IM'
associated with the arch support. As above, as a result of the signs of the
bending
moments, bending moment RMM includes a negative bending moment NBM at the
shoulders of the arch which is greater than the negative moments NM' at the
shoulders but a reduced positive (sagging) bending moment SM' at the crown of
the
arch. As discussed above, due to the signs of the moments, the total of (BM 1'
+
BM2') is less than BM 1'. Prestressing the arch also reduces the sensitivity
of the arch
to outward displacement of the arch footings.
Figure 30 illustrates one means for prestressing the arch. As shown in Figure
30, an element 80 is interposed between the arch footing and the arch. Element
80
prestresses the arch as discussed above. One form of element 80 includes an
inflatable element, such as a hose or other means. Such hose may be inflated
and
pressurized with a setting substance such that compression is induced and
locked
into the arch. As shown in Figure 30, bearing 82 is an arch spring to arch
footing
interface and has a low friction interface 86 between the arch and bearing 82.
The
arch can be the arch as discussed in the aspect of Figures 1 to 14 hereof or
the
composite arch disclosed in the aspect of Figures 15 to 31 hereof. As will be
understood from the teaching of the present disclosure of Figures 15 to 31,
the arch
end arrangement shown in Figure 23 could be applied to both arch ends such
that the
arch can be prestress from both ends.
Figure 31 illustrates another means of prestressing the arch whereby a tie (or
ties) is attached to each end of the arch, and tensioned in order to compress
the arch
(analogous to the string on a bow used for launching arrows in archery).
THIRD ASPECT
With reference to a third aspect of the invention now discussed with reference
to Figures 32 to 51 which have their own reference number sequence which may
overlap with those of Figures 1 to 31, shown in Figure 32 is an arch support
system
such as disclosed Figures 1 to 14. Reference is made to the discussion of
Figures 1 to
14 for a full disclosure of the system shown in Figure 32. However, by way of
CA 02423228 2003-03-20
34
reference, shown in Figure 32 is a system 10 which includes an arch span 12,
which
also will be referred to as an arch element, or simply an arch, which forms
the roof
of a void or open space 14 within an earth filled space. Beneath arch span 12,
walls
16 and 18, which will also be referred to as side walls or retaining walls,
retain
backfilled earth 20 or excavation edges 22 and 24 of previously existing (in
situ)
ground material on either side of void or open space 14 above arch space 12,
overfill
(earth) material OV is placed to create the plane 36. The arch and retaining
walls
may or may not be structurally connected. The art and practice of the present
invention enables the arch and the walls to be constructed independently, in
different
construction phases. The purpose and form of the arch, the retaining walls and
the
means of founding these two key components of the backfilled and/or overfilled
structure will be understood from the teaching of Figures 1 to 14.
Structure 10 can be located between first selected area 30 which can be the
floor of a void or a lower pathway, and which includes a plane 32, and a
second
selected area 34 which can be a roof of a void or an upper pathway which
includes a
plane 36. Arch span 12 and overfill (earth) material OV is placed to create
the plane
36.
The arch span is founded via arch footings 48 and 50 and foundation blocks
40 and 42 on general earth backfill 20 andlor on in situ soil (the surface of
the
previously existing (in situ) subsoil having been excavated to that extent).
Foundation blocks 40 and 42 are each placed behind corresponding sidewalls 18
and
16 respectively of the overfilled and/or backfilled arch structure during its
construction. Arch footings 48 and 50, formed of concrete and/or reinforced
concrete
are interposed between springs 44 and 46 which will also be referred to as
ends of
arch span 12 and the foundation blocks to distribute forces over a wide area
thus also
reducing the strength and stiffness requirements of the solidified fill
material of the
foundation blocks.
As discussed relative to Figures 1 to 14, the foundation blocks distribute the
concentrated arch support forces at the springs of the arch via arch footings
onto a
sufficiently large earth backfill area such that the bearing pressure on the
volume of
CA 02423228 2003-03-20
(in situ or backfill) earth to which the arch loads are applied does not cause
unacceptable displacements, especially in the horizontal direction.
As is also shown in Figure 32, a roadway R can be located above the system
and can include pavement P with pavement P' located beneath the system.
5 Shown in Figures 33a-33c are examples of the type of systems that can be
formed using the teaching of the present disclosure. As shown in Figure 33a,
the
system can include skew elements SB. As shown in plan view Figure 33b, the
system can include a round bridge RB having a plurality of trapezoidal arch
elements
12T or an angled system AB with one trapezoidal element 12T'. Plan views of
10 different arch structures are shown in Figures 34a, 34b and 34c as curved
elements
CB, skew elements SE and straight elements STE.
As discussed above, the method embodying the present aspect of Figures 32
to 51 forms the arch elements in a use orientation. The use orientation for
arch
element 12 is shown in Figure 32; whereas, a side on orientation would have
arch
15 element 12 oriented at a 900 angle with respect to the orientation shown in
Figure 32.
As also discussed above, forming the arch elements in the use orientation
produces
several advantages over forming the arch element in a side-on orientation. A
formwork 60 is shown in Figure 35 in plan view and can be used to form the
straight
elements STE, and/or the skew elements SE and/or the trapezoidal elements TE.
The
20 skew elements can include an angle a. Formwork 60 can include walls, such
as 62,
to define the desired shapes as well as outer perimeter walls 64. Materials
and
procedures suitable for forming the arch elements are carried out using the
formwork
and suitable procedures. The formwork is very simple and no counter forms are
usually required. The formwork can be lifted up or down on one side of the
form as
25 indicated by double-headed arrow 66 in Figure 36 to help in placing and
vibrating
the concrete in the formwork, and to prevent the flow of vibrated concrete by
changing the gradient/slope. The lifting can be performed using a suitable
jack. The
formwork, itself, can be vibrated, and when using the lifting system with
suitable
jacks, the vibration of the formwork can be done in halves or thirds of the
arch
30 element.
CA 02423228 2003-03-20
36
Once the concrete is poured and has hardened, the elements are moved, in the
use orientation, from the formwork to a yard for stacking and from there to a
transportation vehicle using a crane or the like. As shown in Figures 37a and
37b, an
element 12X is attached to a crane (not shown) by a harness 68 which includes
two
cables 70 and 72 attached to a first surface 74 of element 12, As element 12,'
is
lifted from the formwork, it will flex under its own weight from an unflexed
configuration 12,,, as shown in solid line in Figure 37a to a flexed
configuration 12X2
shown in dotted lines in Figure 37a. This flexing can be used to obtain the
desired
pre-deformation to prestress the arch to partly or wholly compensate the
influence of
a possible outward yield (deformation) of the foundation blocks when the arch
is
subjected in its final position to loading. The arch elements are placed in
their pre-
deformed shape (indicated in dotted line in Figure 37a) and return to their
original
shape (indicated in solid line in Figure 37b) when overfilled. When the
elements
with the dotted line shape are placed onto the foundation blocks, the
foundation
blocks will hardly move under the dead weight of the arches only. When all
elements
have been placed, the overfill is placed which then has a total weight greater
than
that of the elements alone. This loading condition, the overfill plus the arch
dead
weight, produces a considerable horizontal thrust are on the foundation
blocks. If the
foundation block, or blocks, is/are not as stiff as desirable, this loading
may push the
foundation blocks out by a small amount. Even small movements result in the
activation of the earth resistance to a considerable degree preventing further
movement of the foundation block. Ideally, the foundation block will move out
about
as much as the ends of the arch elements have been drawn together by the pre-
deformation before installation. If this is the case, the moments introduced
by the
drawing together of the ends and the opposite moments caused by the outward
deformations of the foundation blocks will largely cancel each other out so
that the
elements - before traffic loads are applied - are in a state of very little
moments. This
helps to overcome disadvantages created by a certain amount of yielding of the
foundation blocks. Should the foundation blocks not yield, the prestressing or
pre-
deformation is not harmful because it is done only to a degree which is within
the
CA 02423228 2003-03-20
37
allowable limits of the arch design. Furthermore, the moments generated by
prestressing are opposite in direction to the majority of moments generated by
traffic
and are therefore not detrimental to the load carrying capacity of the arch.
Prestressing of the arch element can also be effected by structural elements,
such as tie rod 80 shown for arch element 12ic2 . Tie rod 80 can include a
turnbuckle
82 or the like to set the desired amount of camber, or pre-deformation on the
arch
element.
As discussed above, in some instances differential displacement can occur
between adjacent arch elements in a system having a plurality of arch
elements. This
differential deformation can be prevented, or at least minimized, by
connecting
adjacent arch elements together once they have been put in place. The
connection
can transfer shear forces between elements and thereby reduce the relative
displacements to zero or almost zero. Additionally, the load carrying capacity
is
increased since two or more adjacent elements carry the imposed loads in
unison.
The method embodying the aspect of Figures 32 to 51 of the present invention
includes connecting adjacent elements in one of several different ways.
The first connection is via post-tensioning one or several of the tie
elements.
This can be effected by introducing tension braces to the tie elements. The
post-
tensioning force creates friction between the adjacent elements which in turn
provides shear resistance. The shear resistance prevents and counteracts
differential
deformation between adjacent arch elements.
A second form of connection is by bolting. Bolting is indicated in Figures 39
through 44. Holes, such as hole 90 are provided through each arch element. The
holes can be defined by placing pipes in the formwork during formation of the
arch
element. The holes can have a counterbore 92 on each end thereof. The holes in
each
arch element are located so that the holes in one arch element will be aligned
with
the holes in an adjacent arch element as shown in Figure 41 for adjacent arch
elements 12,,a1 and 12xa2. A relatively thick steel rod or dowel bar 94
(reinforcement
bar) is positioned in the aligned holes such that it extends through the holes
in at
least two adjacent arch elements. To ensure centricity of the rod, support
elements 96
CA 02423228 2003-03-20
38
can be located in the arch elements inside the holes. To guarantee a tight fit
and
proper load transfer, the rod has a sheath 98 surrounding it which can be a
thin but
tough plastic sheathing. After placement of the rod the sheath is filled with
grout
(cement plus the sand (or filler) plus water) under pressure. The grout fills
the
interspace between the rod and the arch element adjacent to the holes. The
grout
prevents play between the rod and the arch element. The rod or dowel bar
becomes,
after hardening of the grout, an integral part of the arch element. A space 99
exists
between the sheath and the arch element adjacent to the hole and is filled
when the
sheath expands after insertion of grout under pressure. At ring joints, such
as ring
joint RJ (see Figures 34a to 34c), the bar or rod continues between elements.
Here
also it is surrounded by grout which protects it against corrosion. Since the
sheath
extends for the entire length of the rod or dowel bar, the grout will not leak
out of the
sheath before setting. The sheath will expand to snugly fit the hole (or
holes). At the
joints between the elements, such as joint 102, the sheath prevents the grout
from
leaking out. Additionally, as shown in Figure 13, caulking 104 can be applied
at the
joints to make the structure watertight.
It is also noted that in order to produce a bridge from precast elements, it
has
to be done in several pieces which are each smaller than the entire bridge.
These
pieces (elements) can be tied together on site using the dowel and grouting
system
discussed above.
It is also noted that due to the rods or dowels the precast arch bridge of
Figures 32 to 51 performs almost as well, deformation and resistancewise, as
if the
joint (the ring joint) didn't exist as would be the case with a cast-in-place
structure.
The whole bridge acts as a homogeneous vault and not a number of individual
arch
elements, one next to the other. Thus, the rods or dowel bars are an effective
means
to overcome the drawbacks of precast structures which are separated by joints
instead of being homogeneous structures like cast-in-place structures.
Still further means can be used to connect adjacent arch elements. Such a
further means is indicated in Figure 45 and includes a cam 110 in one arch
element
and a corresponding depression 112 in an adjacent arch element. Each arch
element
CA 02423228 2003-03-20
39
contains both cams and depressions. A cam on one elements is accommodated in
an
associated depression on an adjacent element to connect the two adjacent
elements
together. Adhesive can also be applied to the cam and/or to the depression to
provide
a permanent connection free of play.
The foundation of the precast arch element (Figures 32 to 51) is, in
principal,
the same as the foundation disclosed in the figures 1 to 14. The foundation
will
include the foundation block. The arch elements can include an arch footing
such as
indicated in Figure 32 as arch footings 48 and 50. In the means and method
embodying the present invention, the arch footings can be precast together
with the
arch element as indicated for arch footing 50p in Figure 49 which rests
directly on
the foundation block. Another form of the arch footing is shown in Figure 50
as arch
footing 50p1 which is cast in place and connected to the arch element which
does not
contain precast footings. Yet another form of the arch footing is shown in
Figure 51
as arch footing 50P2. Arch footing 50p2 includes a small footing 50pT that is
precast
with the arch element and a layer of cast-in-place concrete 50pT, between the
precast
footing and the foundation block. This procedure allows the precast footing to
be
designed quite small (thus adding only little weight to the precast element)
while the
concrete (preferably unreinforced) which is cast-in-place between the precast
element and the foundation block spreads the footing forces sufficiently to be
borne
by the solidified earth material of the foundation block. This cast-in-place
concrete
would be poured after the precast elements are installed in their final
position, the
latter being provisionally supported on locally protruding parts of the arch
element
LPP in Figures 3a to 3c or element 124 of Figure 16. This ensures that the
final
support will be between the larger part of the arch element and the foundation
block
via the cast-in-place concrete.
This process of placing cast-in-place concrete between the arch element and
the foundation block is indicated in Figures 46 to 48 in which arch element
120 has
an end area 122. An element 124 extends out of the end area of the arch
element and
engages the foundation block when the arch element is initially installed.
Reinforced
or unreinforced concrete 126 is then cast in place around the arch element end
and
CA 02423228 2003-03-20
the foundation block and overfill 128 is subsequently placed on the cast-in-
place
concrete once this has hardened. Concrete can also be located between the end
of the
arch element and the foundation block as indicated in Figure 36 by cast-in-
place
concrete 130.
s As used herein with reference to Figures 32 to 51, the term "prestressing"
refers to the condition of an arch element such as shown in Figures 37a and 38
prior
to placement of the arch element in the system; and the term "post-tensioning"
refers
to a condition of an arch element after it has been placed. Thus, the elements
shown
in Figures 37a and 38 are prestressed; whereas, adjacent arch elements 12 can
be
io post-tensioned by the action of the dowel rods or by the action of friction
of one arch
element on an adjacent arch element or by the interlocking action of the
elements
shown in Figure 45.
It is understood that while certain forms of the invention have been
illustrated
and described herein, it is not to be limited to the specific forms or
arrangements of
15 parts described and shown.
